1. Field of the Invention
The present invention relates to the cleaning and reclamation of machinery coolants. More particularly, the present invention is a method and apparatus for removing of metal fines and tramp oils from used synthetic and semi-synthetic coolant for recycle.
2. Discussion of Background
In metalworking various water-based, synthetic and semi-synthetic coolants are used to remove the heat generated by the performance of mechanical work on a metal piece, the "work piece". Metal working includes drilling, turning, drawings, forming, sawing, grinding, milling, tapping, threading, honing, broaching and other operations. Synthetic and semi-synthetic coolants are water-based lubricants that usually contain no petroleum oils but, rather, non-petroleum additives such as polyalkylene glycols. The synthetic coolants may contain other ingredients such as anti-foaming agents, rust inhibitors, biocides and extreme-pressure inhibitors.
As a result of these operations, the coolants become contaminated with metal fines and "tramp oils", from machine hydraulic fluids finding their way into the coolant stream. When the levels of fines and tramp oils become high enough, the coolant will no longer adequately serve its intended purpose and must be disposed of or cleaned.
Various devices exist to clean coolant. Many of these include cannisters containing a filter medium or bag filters. Some include settling tanks or ponds to allow heavier particulate to settle out. These devices are slow, inefficient and result in material other than the fines alone that will require disposal, such as the filter media.
Disposal of contaminated metalworking fluids is not a simple nor inexpensive matter. These fluids are hazardous and special disposal techniques are mandated by law to provide suitable long term storage or treatment so that the hazards of these fluids remain separated from the environment. Attendant with the physical disposal requirements are requirements for record-keeping and chemical analysis. Consequently, reduction of the volume of waste has become a goal of metalworking facilities to reduce disposal costs. Ideally, coolants would be repeatedly reclaimable or reconditionable for reuse and the fines and tramp oils separable so that no coolant is lost in the process of reclaiming and the quantities of fines and tramp oils remaining in the cleaned coolant would be negligible.
Several attempts have been made to provide devices for cleaning and reclamation of coolants. A portable apparatus is described by Love in U.S. Pat. No. 4,772,402. His apparatus includes two centrifugal pumps and an accumulator reservoir. The first pump draws coolant from the machine, discharging it into a coarse filter in the reservoir. The second centrifugal pump draws coolant from the reservoir, forces it through a fine filter, preferably containing activated charcoal, and then discharges it into the machine coolant system.
In U.S. Pat. No. 4,636,317, Lewis describes a somewhat different system for processing coolants. Lewis employs a high speed disk-bowl centrifuge in combination with hydrocyclone centrifugation to remove contaminants from oil-and water-based coolants. Wolde-Michael describes a multi-step process including, settling, skimming, centrifuging, and recirculating.
No apparatus in these references disclose a device that has the characteristics of the ideal reclamation system. None removes particulate of submicron size in a portable unit with minimum disposable volume per gallon of coolant processed.